Health officials have sent out more than 2,900 emails and letters to people who may have been exposed to the deadly hantavirus that has infected at least six visitors (two fatally) to a Yosemite campsite in California, but they may have missed opportunities twice over the past five years to mitigate the threat.

In 2007, scientists wrote a report on “Vector-Borne Diseases in California” for the state Department of Public Health that explicitly recommended that Yosemite officials activate a prevention program to warn staff members and park visitors about the virus threat and conduct “active rodent removal programs within buildings and developed areas.” 

The Center for Investigative Reporting says there is no evidence that the recommendation was implemented.

Three years later, a report by the department gave an overall hantavirus risk assessment score of 4.0 (moderate risk, on a scale of 1 to 5) to Yosemite’s Tuolumne Meadows and recommended that it would be prudent to provide each cabin with information on the danger along with warnings to minimize contact with rodents that carry the virus and to report any signs of rodent intrusion, such as droppings and chewed items.

The 2010 assessment was triggered after a woman contracted the virus in June after staying in a tent cabin, similar to ones inhabited by the latest victims. She was hospitalized for three days, but survived. Cleanup crews found deer mouse droppings and nests in wooden interior walls.

Yosemite officials are saying visitors who stayed in one of the 91 “Signature Tent Cabins” at Curry Village between June and August may have been exposed to the virus,  which is spread by contact with rodent feces, urine and saliva, or by inhaling their airborne particles. The park has closed the cabins and is making repairs to better keep rodents out. The cabins were built in 2008.  

A spokesman for the park, noting the rarity of hantavirus infection, told a Bay Area News Group reporter that authorities had to balance people’s need to know with the danger of “creating panic or fear.”

–Ken Broder

To Learn More:

Two More Yosemite Hantavirus Infections Reported as Park Closes 91 Tent Cabins over Exposure Concerns (by Sandy Kleffman, Bay Area News Group)

Yosemite Officials Broaden Hantavirus Notification Effort (by Kate Mather, Los Angeles Times)

Yosemite Officials Say 1,700 Visitors May Have Been Exposed to Hantavirus (by Sandy Kleffman, Bay Area News Group)

Yosemite Officials Say 1,700 Visitors Risk Disease (by Tracie Cone, Associated Press)

Calif. Scientists’ Calls to Warn Yosemite Visitors of Virus Went Unheeded (by Christina Jewett, Center for Investigative Reporting)

Vector-Borne Diseases in California (California Department of Public Health) (pdf)